1. Field of the Invention
The present invention relates to a probe (in particular, a cantilever type probe), a probe card, and a testing device. More particularly, the present invention relates to a probe, a probe card, and a testing device, especially suitable for testing a through hole (a via or a contact hole) to be filled with conductor, and which is provided in a circuit board, a wafer, or the like (hereinafter, referred to as “circuit board”).
2. Description of the Related Technology
As illustrated in FIG. 19, a probe card 152 is used to conduct a short/open test on wiring 151 in a wafer or a circuit board 150. In some cases, a cantilever type probe 153 is adopted as the probe card 152. The probe 153 is provided so as to be precisely positioned in relation to the probe card 152. It should be noted that some probe cards have spring type probes (not shown) provided thereto.
The conventional cantilever type probe 153 has, as illustrated in FIG. 20, a tip side which is bent in a direction away from the probe card 152, thereby a linear contact portion 154 is formed. The contact portion 154 is formed in relatively thin. A rectangular portion 155 which is rectangular in section is provided to the tip of the contact portion 154.
In performing a test on the circuit board 150 using the probe card 152, the contact portion 154 of the probe 153 is brought into contact with the wiring 151 of the circuit board 150, and the probe card 152 further descends by a small distance. This makes the probe 153 elastically deformed to cause the contact portion 154 to slide a little over the wiring 151 in a longitudinal direction (in an X direction in FIG. 19) of the probe 153.
At this time, an oxide film formed on a surface of the wiring 151 is scraped off by the rectangular portion 155 of the contact portion 154, thereby attain stable electrical contact between the contact portion 154 of the probe 153 and the wiring 151.
[Patent Document 1] JP 11-51970 A
[Patent Document 2] JP 56-56646 A
[Patent Document 3] Japanese Utility Model Application Laid-open No. Hei 5-92749
[Patent Document 4] Japanese Utility Model Application Laid-open No. Hei 6-40869
However, when the probe card 152 having the conventional cantilever type probe 153 is used for testing a through hole provided in a circuit board and to be filled with the conductor to test how well it is filled with conductor the following problem arises.
FIG. 21 shows the circuit board 150 having a contact hole (via) 157 provided thereto. This contact hole 157 is formed by filling a through hole 158 with a conductor 159 to hole 158.
It should be noted that, descriptions of the conventional probe will be made on the premise that plating 160 is provide to an inner surface of the through hole 158 and a rear surface 150b of the circuit board 150. In reality, a front surface 150a and the rear surface 150b of the circuit board are provided with wiring connected thereto.
By providing the contact hole 157, the wiring (not shown) provided on the front surface 150a and the rear surface 150b of the circuit board 150 can be electrically connectable. Further, a space between the front surface 150a side and the rear surface 150b side of the circuit board 150 can be kept as hermetic.
When the probe card 152 is used for testing how well the contact hole 157 is filled with the conductor 159, the probe card 152 and the probe 153 are disposed, for example, on the side of the front surface 150a of the circuit board 150. Then, the contact portion 154 of the probe 153 is brought into contact with the conductor 159. With this state, the resistance between the front surface 150a and the rear surface 150b of the conductor 159 and the resistance of a plating 160 provided on the inner periphery of the through hole 158 are measured with the probe 153.
At this time, when the through hole 158 of the contact hole 157 is completely filled with the conductor 159, electric current for the measurement flows through both the plating 160 provided on the inner surface of the through hole 158 and the conductor 159, which relatively reduces the resistance.
On the other hand, when the through hole 158 is hardly filled with the conductor 159 as illustrated in FIG. 22, or, when the through hole 158 is only partly filled with the conductor 159 as shown by the double-dashed chain line is FIG. 22, the electric current for the measurement flows through only the plating 160 provided on the inner surface of the through hole 158.
Therefore, when the through hole 158 is hardly filled with the conductor 159, the resistance is relatively high as compared with a case where the through hole 158 is completely filled with the conductor 159. When only a part of the through hole 158 is filled with the conductor 159, the resistance is higher than that when the through hole 158 is completely filled with the conductor 159, and lower than that when the through hole 158 is hardly filled with the conductor 159.
Here, when the through hole 158 of the contact hole 157 is hardly filled with the conductor 159 or only a part of the through hole 159 is filled with the conductor 159 as described above, there is a possibility that the contact portion 154 of the probe 153 enters the through hole 158 as illustrated in FIG. 22.
When the contact portion 154 of the probe 153 has entered the through hole 158 as described above, there is a possibility that the contact portion 154 might be brought into contact with the lower portion side of the plating 160 in the through hole 158 or with a support 161 for supporting the circuit board 150, provided that the thickness t of the circuit board 150 is thin or the length of the contact portion 154 of the probe 153 is relatively longer with respect to the thickness t of the circuit board 150 (as shown by a broken line).
In such a case, the resistance measured by using the probe card 152 is lower than the actual resistance. More specifically, a problem arises that, although the through hole 158 is hardly filled with the conductor 159 or the through hole 158 is only partly filled with the conductor 159, the result of measuring the resistance would be similar to that of a case where the through hole 158 is completely filled with the conductor 159. As described above, the conventional probe 153 has a problem that it can not accurately measure how well the through hole 158 is filled with the conductor 159.